In order to examine a liquid sample in an NMR spectrometer, in the majority of cases, the liquid is inserted into an elongated narrow tube which is is placed in the strong magnetic field of the spectrometer. In high resolution spectroscopy, in order to average out the effects of inhomogeneities in the magnetic field the sample tube is caused to spin about its axis while mounted in a spinner apparatus which is very accurately positioned in respect to the magnetic field. The sample tube may be up to one foot in length. Such a system is disclosed in U.S. Pat. Nos. 2,960,649 and 3,681,683 assigned to the assignee of the instant application.